The semiconductor chip package technology gradually becomes a constraint factor for developing a more efficient semiconductor chip package. Package designers always struggle against catching up with the pin count increase, dimensional limitation, profile mounting constraint and other requirements developed gradually for packaging and associating integrated circuits. Referring to FIG. 1, it depicts a conventional semiconductor chip package, a Ball Grid Array (BGA) package 100. It comprises at least a semiconductor chip 102 disposed on a substrate 104 and connected electrically to bonding pads 105 of the substrate 104 by a wire bonding method, a plurality of arrayed solder ball pads 106 formed on the substrate 104 to combine with solder balls 108 and a package body 110 enclosing the chip 102 and wires 112 (made by wire bonding). The package 100 is mounted to a printed circuit board (not shown in the figure) by the plurality of solder balls 108. The solder ball 108 is formed on the package 100 or the solder ball bonding pad of the printed circuit board and melted by heating (reflowed) to have the package 100 soldered to the printed circuit board.
For more details, referring to FIG. 2, the surface of the substrate 104 usually has a solder mask 202 covering the substantially whole surface of the substrate 104, and there are only bonding pads 105 exposed from the solder mask. The bonding pads 105 are made of copper and have a metal thin deposition layer 204, including a nickel layer 204a and a gold layer 204b formed on their surfaces. When the substrate 104 is made by the gold pattern plating (GPP) process, the bonding pads 105 are formed through etching a copper layer with a mask of the metal thin deposition layer 204. During the etching process, the over etching phenomenon is generally found, which leads to the metal thin deposition layer 204 protruding over the bonding pads 105 so that part of the metal thin deposition layer 204 is not supported by the bonding pads 105. When the substrate 104 is in the electrical testing or wire bonding process, the bonding pads 105 will be pressed and stretched, and the metal thin deposition layer easily collapses, peels and even breaks.